Highly efficient and reproducible planar perovskite solar cells with mitigated hysteresis enabled by sequential surface modification of electrodes

Fullerene-based derivatives passivation and TiCl4 treatment are widely used as interfacial modification methods in planar perovskite solar cells for enhancing efficiency, stability and reducing hysteresis. Although the two kinds of surface modifications have been separately reported to modify the metal oxide or even directly modify the electrodes, the resulting device performance is still moderate. Herein, we report a sequential surface modification of FTO by combining a low-temperature processed ultrathin TiOx layer with a PCBM passivation layer, synergistically affording high efficiency and mitigated hysteresis and exhibiting good reproducibility for n-i-p planar perovskite solar cells. Based on this sequential modification strategy, the modified FTO substrates can effectively facilitate electron transfer and suppress interfacial recombination. As a result, we obtain efficient perovskite solar cells with the best power conversion efficiency (PCE) of 18.26% and the stabilized PCE of 17.22%. Additionally, we demonstrate that this facile sequential surface modification method gives rise to highly reproducible device performance with the average PCE of 17.16%. Beyond that, the photocurrent hysteresis is effectively suppressed for the obtained solar cells compared with the single modified analogues owing to facilitated electron transfer at the interface.